Nuclear power generation is made by a method for turning a turbine using energy generated at the time of nuclear fission to generate electric energy. FIG. 1 schematically illustrates a principle of typical nuclear power generation. An enormous amount of heat energy is generated by the nuclear fission of nuclear fuel within a pressure vessel (or referred to as a reactor vessel). The heat energy is transferred to a coolant within the pressure vessel and the coolant is circulated to be released from the pressure vessel and to be reintroduced into the pressure vessel via a heat exchanger, as illustrated by a thick arrow in FIG. 1. The heat energy of the coolant is transferred to a steam generator while passing through the heat exchanger and water within the steam generator is converted into high-temperature and high-pressure steam due to the heat energy. The so generated high-temperature and high-pressure steam is supplied to the turbine as illustrated by a thin arrow in FIG. 1, the turbine rotates by power of steam, a generator connected to the turbine rotates together, thereby generating power. The steam from which the energy is lost by the rotation of the turbine again goes through the phase change to be converted into water. As illustrated by the thin arrow in FIG. 1, the water is reintroduced into the steam generator and is thus circulated.
FIG. 1 illustrates only systems which are a subject of the nuclear power generator. Actually, the reactor is essentially provided with the safety system. As described above, very high heat is generated when the reactor is operated. The high-heat environment includes a very high risk to cause disaster when the reactor is damaged. Therefore, when the reactor is damaged, the safety system should be essentially provided to quickly cool the reactor.
Therefore, the related art includes various types of safety systems which may safely cool the reactor at the time of the accident of the reactor. Describing in more detail, the safety system which is applied to the existing reactor may include components (ex. passive residual heat removal (PRHR) system, etc.) which circulate the coolant accommodated in the reactor vessel to the outside, components (ex. core make-up tank (CMT), safety injection pump (SI pump), etc.) which supply the coolant separately accommodated in the outside to the vessel), etc. The example is illustrated in FIG. 2. Further, all of the safety systems of the foregoing example use the coolant (water) to perform the cooling. To more increase cooling efficiency, the configuration of the safety systems which simultaneously use air and water is also disclosed. As an example of the safety system technology of diversifying a heat sink using air and water, there are Japanese Patent Laid-Open Publication No. 2010-217091 (“Containment Vessel Passive Cooling System And Liquid-Metal-Cooled-Reactor”), Korean Patent Laid-Open Publication No. 2009-0021722 (“Air/Water Hybrid Passive Reactor Cavity Cooling Apparatus And Method For Core Decay Heat Removal Of High Temperature Gas-Cooled Reactor”), etc.
However, research and development for more improving efficiency of a reactor driving system have been continuously conducted and therefore only the typical safety system may not obtain the sufficient cooling efficiency. Further, if the safety system is configured to be operated by receiving a separate control command even at the moment of urgent accident like the damage of the reactor, there are many risks that the safety system malfunctions due to the damage of the control system and thus the safety system is not properly operated, an operator of the reactor does not issue the control command in time, etc. In addition, as described in the foregoing related arts, since the structure of the reactor safety system is very complicated and multiplexed, design factors to be considered to construct facilities are too many and thus it is very difficult to design and actually construct the safety system and even after the facility construction is completed, ones to be tested or monitored are too many for safe operation and thus it is difficult to operate and control the safety system.
Therefore, a need exists for the reactor safety system which may more improve the cooling efficiency than that of the existing safety system, may be completely passively operated without performing the separate control operation of the operator, and may have a simpler structure than the existing reactor safety system.